Main-sequence luminosity and initial mass functions of six Magellanic Cloud star clusters ranging in age from 10 megayears to 2.5 gigayears

Abstract

view Abstract Citations (140) References (120) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Main-Sequence Luminosity and Initial Mass Functions of Six Magellanic Cloud Star Clusters Ranging in Age from 10 Megayears to 2.5 Gigayears Mateo, Mario Abstract Deep CCD B and V frames of six star clusters in the Magellanic Clouds (MCs) have been analyzed in order to determine the main-sequence mass functions for the stars in these systems. The clusters span a range in age from 10 Myr to 2.5 Gyr and a range in metallicity from about solar to 1/20th solar. The procedures used to determine the cluster luminosity functions are described in detail. In particular, the counting incompleteness depends sensitively on position on the CCD frame and magnitude, and the appropriate corrections have been empirically determined and applied to convert the observed star counts to "true" luminosity functions (LFs). These LFs were converted to mass functions (MFs) via mass-absolute magnitude relations based on theoretical isochrones that were "fitted" to the cluster color-magnitude diagrams. Both the "classical" models of VandenBerg, Becker, and Brunish and Truran and the "overshoot" models of Bertelli et al. were used in this analysis. Arguments are presented that the observed MFs of the program clusters are very similar to their initial mass function (IMFs). The shapes of IMFs of the six clusters are indistinguishable in the range 0.9-10.5 M_sun_, and there is no reason to reject the hypothesis that the IMFs of the six clusters were drawn from a single power-law IMF with a slope x = 2.52 +/- 0.16, where IMF is proportional to M^-(1+x)^ and M is the stellar mass. This result does not depend significantly on the adopted MC distance scale, or whether "classical" or "overshoot" stellar evolutionary models are used in the analysis. There is some indication that the high-mass end (i.e., log M >~ 0.45) of the average IMF of the six clusters is slightly shallower than the low-mass end. Comparisons with previous work on the MFs of Galactic open clusters shows rough agreement, although the MC cluster MFs do not show the large scatter observed in open clusters. The average IMF of the program clusters is remarkably similar to the solar neighborhood IMF determined by Scalo, and the MC cluster IMF slope is similar to some recent findings for high-mass stars in the LMC. A comparison of the present results with the elegant bimodal IMF model of Larson shows poor agreement. Publication: The Astrophysical Journal Pub Date: August 1988 DOI: 10.1086/166552 Bibcode: 1988ApJ...331..261M Keywords: Globular Clusters; Magellanic Clouds; Main Sequence Stars; Stellar Evolution; Stellar Luminosity; Color-Magnitude Diagram; Metallicity; Stellar Mass; Astrophysics; CLUSTERS: GLOBULAR; CLUSTERS: OPEN; GALAXIES: MAGELLANIC CLOUDS; LUMINOSITY FUNCTION; STARS: EVOLUTION; STARS: STELLAR STATISTICS full text sources ADS | data products SIMBAD (6)